Multiplication

Date: 02/11/99 at 17:37:23
From: Karen Tornquist
Subject: Multiplication
How many decimal places should there be in this problem?
3.26
x 0.25

Date: 02/12/99 at 10:51:07
From: Doctor Micah
Subject: Re: Multiplication
Thanks for writing to Dr. Math. Decimals can be tricky, but once you
learn the rules they aren't so bad. I assume you already know how to
multiply two large numbers, such as 327 * 45. If you don't, please
write back and we'll explain that also. If you do know how, then
multiplying decimals is easy. Just forget about them and do the
multiplication the way you normally would for two big numbers. Then add
the number of decimal places in each of the numbers you started with.
This is how many places from the right you should place the decimal in
your result.
Here's an example:
4.25
x 1.53 Now, just leave out the
------ decimals and multiply normally.
425
x 153
-----
1275
21250
+ 42500
-------
65025 Now since 4.25 had two decimal
places and 1.53 had two decimal
places, the answer should have
2 + 2 = 4 decimal places. So:
4.25
x 1.53
-------
6.5025
The only time it's tricky is when your answer ends with zeroes. You
have to be sure not to drop the zeroes before you put in the decimal
point:
0.45
x 2 Do the same thing; just forget about
----- the decimal and multiply.
45
x 2
----
90 Now, the answer should have
0 + 2 = 2 decimal places. So:
0.45
x 2
-----
0.90 AFTER you add the decimal point,
you can drop the ending zeroes. So:
0.45
x 2
-----
0.9
I hope you can do your own problem now. If you still have trouble,
please feel free to write back to Dr. Math.
Good luck,
- Doctor Micah, The Math Forum
http://mathforum.org/dr.math/